A gas turbine engine is a flow machine in which a pressurized gas expands. The gas turbine includes a turbine or expander, a compressor connected upstream of the turbine, and a combustion chamber between the compressor and turbine. Expanding gas produced in the combustion chamber drives blades of the turbine which provides power for the compressor and other engine output. The compression of air by way of the blading of one or more compressor stages subsequently mixes the compressed air in the combustion chamber with a gaseous or liquid fuel, where the mixture is ignited by an igniter to initiate combustion. The combustion results in a hot gas (a mixture composed of combustion gas products and residual components of air) which expands in the following turbine section, with thermal energy being converted into mechanical energy in the process to drive an axial shaft. The shaft is connected to and drives the compressor. The shaft also drives a generator, a propeller or other rotating loads. In the case of a jet power plant, the thermal energy also accelerates a hot gas exhaust stream, which generates the jet thrust.
At startup, the igniter is operated to ignite an air-fuel mix under ambient temperatures and ambient pressure. During operation of the gas turbine engine, flameout conditions can occur, at which time the igniter is operated to re-ignite the air fuel mix which is under relatively hot and high pressure conditions. For example, controlled flameout occurs during a so-called trip, which is a fast shutdown effected by interruption of the fuel supply to the combustors and implemented as a consequence, for example, of exceeding a threshold value for an operating parameter such as the rotational speed being exceeded. Igniter failure can render an engine inoperable and cause unplanned or inopportune shutdowns of a power plant or vehicle. Such shutdowns are unwanted and can lead to high costs and other severe consequences
Current approaches to monitoring the health of igniters involve physical inspection during periods of shutdown for routine maintenance. However, damage may be difficult to observe and imminent failure problematic to predict.